There has always been interest in collecting and shooting weapons that have been developed for and used by the military, both handguns and rifles. This interest is held by many civilians, particularly those who served in the military. Because many of the firearms are capable of fully automatic fire, private ownership is both a right and a privilege and is available to qualified, law-abiding individuals who, in accordance with federal law, acquire a Class II or III Firearms Dealer license or those individuals who apply for and obtain the requisite permission from the local authority where they reside and the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) to become the registered owner of a NFA (National Firearms Act) firearm.
Semi-automatic firearms, on the other hand, are not subject to as rigorous a procedure to own and fire legally and in fact, can currently be legally transferred between individuals. While there is a good selection of handguns and rifles capable of semi-automatic operation, including some “civilian” versions of military firearms, original fully automatic firearms are not readily available in semi-automatic versions. The reasons are numerous including cost of the original firearm, costs to convert it, the necessity for a gunsmith or armorer to perform the work and, the realization on the part of one who has legally acquired such a firearm that the value is often seriously diminished by conversion to semiautomatic operation. Notwithstanding the foregoing reasons, there is a desire for original firearms that have been legally converted to semi-automatic operation and are thus, more readily acquired.
This invention involves the conversion of an M240 automatic rifle to semi-automatic fire. The M240 is a gas operated, air cooled automatic firearm. Expanding gases from the ignition of powder in the cartridge furnishes the energy for the operation or cycling of the rifle. Immediately after firing, as the bullet traverses the barrel and passes an internal gas port prior to exiting from the muzzle, the live gases expand through the gas port into the gas tube or cylinder to impinge against the head of a piston. In so doing, the piston within the gas cylinder is forced rearwardly, toward the buttstock, driving an operation rod assembly (herein “op rod assembly”) which cycles a combination of internal components while compressing a recoil spring that effects the return movement.
The op rod assembly carries the firing pin and a bolt link pivotally secures the op rod to the bolt lock. As the op rod assembly begins to travel rearwardly under the influence of the expanding gases resulting from the firing of a cartridge, the bolt link rotates and pulls the bolt lock up out of its cradle in the receiver, thereby unlocking the bolt from the receiver. Once free from the mating receiver surfaces, the bolt travels rearwardly with the bolt link and op rod assembly as it continues its rearward travel. In so doing, several additional operations continue. Cartridges for the M240 are belt fed, and the bolt carries a roller that engages a feed lever to feed cartridges into the receiver in a known manner, during this rearward travel. The op rod assembly contacts a buffer in the buttstock, halting its rearward movement, and immediately begins return travel in response to the compression of the recoil spring. Continued forward movement is then a function of the position of the trigger.
Assuming the trigger remains depressed, it will not engage the sear ledge on the underside of the op rod assembly and thus the op rod assembly will continue forward under the influence of the recoil spring. During the forward movement, the bolt strips a cartridge from the belt for chambering. Because they are associated with the op rod assembly, the bolt, bolt lock and bolt link also move forward until the very last increment of movement. The bolt moves until the cartridge is seated, which limits the forward movement of the bolt so that the bolt link is caused to rotate downward, lowering the bolt lock into locking engagement with the receiver, at which stage, the bolt cannot move rearwardly. Directly thereafter, the firing pin carried by the op rod assembly is forced to strike the primer of the chambered cartridge, thereby firing it whereby the above firing sequence is repeated in response to sustained depression of the trigger or until the ammunition is exhausted.
Repeat of this cycle is dependent upon the trigger remaining in the fired position. If the operator releases the trigger, the sear is immediately raised into the path of the sear ledge on the reciprocating op rod assembly. In rearward travel, the op rod assembly can push the sear down to pass over it. However, upon the return, the sear is raised by a spring and engages the sear ledge, halting continued forward movement of the op rod assembly. When this occurs, the action remains opened, and no new round is loaded. Accordingly, the M240 rifle is one which fires from the open bolt and, as soon as the trigger is again pulled, the sear is pulled out of engagement with the sear ledge, allowing the op rod assembly to move forward causing all of the foregoing operations. The bolt closes, taking with it a fresh round from the belt, which is simultaneously chambered and instantaneously thereafter fired, as the foregoing sequence is allowed to repeat.
Basically, the art has not provided a facile means or device by which the M240 can be essentially permanently converted to semi-automatic only operation. Accordingly, there is a need for a striking mechanism that is capable of rendering the M240 rifle a semi-automatic firearm. Moreover, to comply with the existing federal laws, such a firearm must meet BATFE approval which is given where the Bureau determines that the firearm is not readily converted back to fully automatic operation.